CVE-2026-68148 (GCVE-0-2026-68148)

Vulnerability from cvelistv5 – Published: 2026-08-10 11:59 – Updated: 2026-08-19 16:30
VLAI
Title
fscrypt: Add missing superblock check in find_or_insert_direct_key()
Summary
In the Linux kernel, the following vulnerability has been resolved: fscrypt: Add missing superblock check in find_or_insert_direct_key() The legacy 'fscrypt_direct_keys' table caches master keys that are used by v1 encryption policies that have FSCRYPT_POLICY_FLAG_DIRECT_KEY. It's just a global table for all filesystems (since the keys can be provided by the legacy process-subscribed keyrings mechanism, which makes it difficult to reuse super_block::s_master_keys). The entries in it ('struct fscrypt_direct_key') do contain a super_block pointer, though, for passing to fscrypt_destroy_inline_crypt_key() when the last inode that references the key is evicted. However, when finding the fscrypt_direct_key for an inode, we weren't actually comparing the super_block pointer. As a result, inodes with different super_blocks could point to the same fscrypt_direct_key. That could extend the lifetime of a fscrypt_direct_key beyond the super_block it points to, causing a use-after-free later. Fix this by creating distinct fscrypt_direct_key structs for distinct super_block structs. Note that this problem doesn't exist in the v2 policy equivalent ("per-mode keys"), since the data structures there are per super_block.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 22e9947a4b2ba255888541bd0111cf00b9b16586 , < 965b5bc8cf5031225e057979ce660fec2bd5fbfc (git)
Affected: 22e9947a4b2ba255888541bd0111cf00b9b16586 , < 330249609b70778094a7a36f5b6bcfa6362121d4 (git)
Affected: 22e9947a4b2ba255888541bd0111cf00b9b16586 , < deff41898a5ae3a47db5fa1896a494aa95efda5d (git)
Affected: 22e9947a4b2ba255888541bd0111cf00b9b16586 , < 95376fe9c145be35566991df99c53134943d992f (git)
Affected: 22e9947a4b2ba255888541bd0111cf00b9b16586 , < 466f187b501a5ac8e1ea2ccf3ccd5c46108d8830 (git)
Affected: 22e9947a4b2ba255888541bd0111cf00b9b16586 , < b5fa40226e71c17847b9ff2816c6ca4133d0d994 (git)
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Linux Linux Affected: 6.1
Unaffected: 0 , < 6.1 (semver)
Unaffected: 6.1.183 , ≤ 6.1.* (semver)
Unaffected: 6.6.148 , ≤ 6.6.* (semver)
Unaffected: 6.12.101 , ≤ 6.12.* (semver)
Unaffected: 6.18.42 , ≤ 6.18.* (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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              "value": "AV:L - The flaw is reached only through local syscalls (mount/umount, FS_IOC_SET_ENCRYPTION_POLICY, and file I/O that calls fscrypt_get_encryption_info -\u003e find_or_insert_direct_key); fscrypt is not invoked from network-facing kernel services.\nAC:L - An attacker who can mount two encrypted filesystems with the same v1 DIRECT_KEY master key, share the global cache entry, then unmount the first superblock can deterministically trigger eviction-time cleanup on a freed super_block without races or victim-dependent timing.\nPR:L - Exploitation requires mounting/unmounting filesystems and setting v1 DIRECT_KEY policies (CAP_SYS_ADMIN in a user/mount namespace) or supplying keys via process keyrings; per kernel guidance, CAP_SYS_ADMIN obtainable in user namespaces maps to PR:L.\nUI:N - No separate victim action is required; the attacker sets v1 DIRECT_KEY policies, accesses encrypted inodes on two mounts, and controls unmount/eviction to hit the vulnerable refcount and cleanup path.\nS:U - The use-after-free corrupts kernel heap memory and enables local privilege escalation within the same kernel; it does not cross VM, hypervisor, or IOMMU security boundaries.\nC:H - Extending a fscrypt_direct_key past its super_block lifetime causes cleanup to dereference a freed super_block in fscrypt_destroy_inline_crypt_key(), a use-after-free that can leak kernel memory and support arbitrary-read exploitation primitives.\nI:H - Use-after-free during inline-crypto key destruction on a dangling super_block pointer can be leveraged for heap corruption and arbitrary kernel writes, enabling local privilege escalation rather than only a controlled crash.\nA:H - Evicting the last inode holding the mismatched fscrypt_direct_key dereferences a freed super_block during key teardown, which can cause kernel oops/panic and complete local denial of service on encrypted mobile/embedded and server systems using inline encryption."
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    "datePublished": "2026-08-10T11:59:13.413Z",
    "dateReserved": "2026-07-30T09:28:09.371Z",
    "dateUpdated": "2026-08-19T16:30:13.417Z",
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      "cve": "CVE-2026-68148",
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      "initial_release_date": "2026-08-10T00:00:00+00:00",
      "product_status:known_affected": "184",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: fscrypt: Add missing superblock check in find_or_insert_direct_key()",
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      "current_release_date": "2026-09-22T16:47:55Z",
      "cve": "CVE-2026-68148",
      "id": "CVE-2026-68148",
      "initial_release_date": "2026-08-18T16:56:06Z",
      "product_status:first_fixed": "60",
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      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-68148",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-68148.json",
      "version": "5"
    }
  }
}



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